Whisk the olive oil, marjoram, vinegar, shallot, garlic, 2 teaspoons of the salt, and pepper in a large bowl.,Add the chicken and turn to coat evenly.,Cover and marinate at room temperature for 1 hour, stirring once, or refrigerate for up to 4 hours.,If you choose to refrigerate, you might want to pour everything into a large zip-top bag to take up less space.,Oil the grill racks.,Preheat your grill using all burners set on high and with the lid closed for 10 to 12 minutes.,Put the pancetta or bacon into a saucepan with enough cold water to cover.,______,Set aside.,Remove the chicken from the marinade and discard the marinade.,Put the breadcrumbs in a shallow bowl and season with the remaining 2 teaspoons salt.,Roll the chicken pieces in the breadcrumbs to coat.,Alternate threading the chicken and pancetta onto the skewers, starting and ending with chicken.,Leave space around the meat so the heat gets to all sides.,Place the skewers on the grill.,Close the lid and grill, turning every few minutes, until the chicken is cooked thoroughly and the breadcrumbs are crispy, 8 to 10 minutes.,Serve hot.